My artist finished our project before she created an Upwork account, and I would like to provide positive feedback. So there is no 'job' to provide feedback on. How can I leave positive comments for the public to see about my artist?
You may create a job, invite your freelancer, sign a contract and end it as finished. After you end the contract, you may leave private and public feedback. However, contracts with no earnings may hurt your freelancer's Job success score. Click this link to know the things that may affect your freelancer's JSS.